The invention relates to semiconductors. More particularly, the invention relates to methods for producing doped polycrystalline semiconductors and to methods for producing doped monocrystalline semiconductors from predoped monocrystalline and polycrystalline semiconductors.
In recent years, electronics has come to be dominated by semiconductor devices, which are found in the discrete devices and integrated circuits of computers, calculators, televisions, VCRs, radios, telephones, answering machines, wristwatches, cameras, and cars, among others. Semiconductor devices are formed from semiconductors, which are compounds having conductivities intermediate between those of the high-conductivity conductors and the low-conductivity insulators. Here, conductivity refers to a compound""s ability to conduct electricity; compounds with greater conductivities are able to conduct greater amounts of electricity.
Semiconductors are important in part because their conductivity readily may be altered by the addition of certain foreign compounds. These foreign compounds are known as dopants, and the addition of these foreign compounds to semiconductors is known as doping.
Doping may be used to create two types of semiconductors: n-type semiconductors and p-type semiconductors. In n-type semiconductors, the dopant adds negative charge carriers, which typically comprise extra electrons. Examples of n-type dopants for silicon-based semiconductors include phosphorus (P), arsenic (As), and antimony (Sb). In p-type semiconductors, the dopant adds positive charge carriers, which typically comprise holes (or missing electrons). Examples of p-type dopants for silicon-based semiconductors include boron (B).
Although doping is essential to semiconductor technology, current doping methods suffer from a number of shortcomings. In particular, current doping methods involve doping monocrystalline semiconductors as they are produced from polycrystalline precursors. Doping monocrystalline semiconductors may involve frequent storing, weighing, and handling of dopant. This processing requires special equipment, which may be bulky and expensive. This processing also requires an operator, which may expose the operator to extremely toxic dopants, such as arsenic. Doping monocrystalline semiconductors also may involve loss or uneven distribution of dopant.
The present invention addresses these and other shortcomings by providing methods for producing doped polycrystalline semiconductors and methods for producing doped monocrystalline semiconductors from predoped monocrystalline and polycrystalline semiconductors. These methods may reduce or eliminate the need to store, weigh, and handle dopant during the production of doped monocrystalline semiconductors. These methods also may enhance the uniformity of dopant distribution.
In a first set of embodiments, the invention provides methods of forming doped polycrystalline silicon. One such method involves (1) providing a reactor for chemical vapor deposition, (2) creating a vapor within the reactor that includes a silicon compound and a preselected dopant, and (3) providing a substrate, exposed to the vapor, onto which the silicon and the dopant in the vapor are deposited to form doped polycrystalline silicon. Additional, related methods are described in the detailed description and claims.
In a second set of embodiments, the invention provides methods of forming a monocrystalline semiconductor having a preselected concentration of a dopant. One such method involves (1) selecting a first amount of a first semiconductor, the first semiconductor having a first concentration of the dopant, wherein the first concentration is higher than the preselected concentration, (2) selecting a second amount of a second semiconductor, and (3) using the first and second amounts to grow the monocrystalline semiconductor. The first and second amounts are selected so that the monocrystalline semiconductor has the preselected concentration of the dopant. Additional, related methods are described in the detailed description and claims.
The nature of the invention will be understood more readily after consideration of the drawings and the detailed description of the invention that follow.